Zulkey herself floated the idea that perhaps the idea was "to match the thing that you eat with a drink, except the relationship between thirst and food doesn't seem to make sense here. A McChicken would probably make you much thirstier than a Salad, and who wants to drink Coke with a parfait?"

One commenter discerned some sort of calorie bargaining system, in which McDonald's is encouraging consumers to rationalize the sugar intake involved in drinking a large soda by ordering a "healthy" salad:

The only thing I can think of is calorie count. Like if you get a parfait, maybe you only want a small drink because the meal already has a lot of calories, but if you get a salad, you might allow yourself to get a large drink because you chose a low-fat/low-cal meal.

This is hard to believe, especially as it would involve the implicit admission that (shock! horror!) a sweetened yogurt parfait from McDonald's is not actually all that virtuous of a dining choice. Indeed, as another commenter noticed, corporate advertising would indeed have plumbed new depths of cynicism if McDonald's really was to just go ahead and publicly say, "You know you're gonna walk out of here consuming 3,000 calories no matter what, so here's an easy visual reference to make sure you get all 3,000 of those calories, regardless of what you order."

Several others (perhaps with tongue in cheek) suggested that McDonald's might be trying to rename its drink sizes:

They're establishing brand names for their drink sizes like Starbucks: "I'd like the QuarterPound McKraken, hold the pickle, and a McChicken Diet Pepsi."

And yet others have projected their own tendency to overthink things onto the ad agency, and suspect a sneaky viral masterplan (one that I am now inadvertently playing into):

I think their ad agency is fucking genius. It features a lot of products that they sell (salad, parfait, chicken, coke); some promotion that's going on ($1 drinks); and, at first glance, makes NO FUCKING SENSE. Why is it good to make no sense? Because analytics get mad, and shop it around to their friends, "Have you seen this new McDonalds ad?" Now the ad's one visual impression is hitting 5 verbal impressions (making up my own terminology here). Whatever agency this is must be composed of master trolls.

The drinks aren't even different sizes, just different depths of field. Weird, weird ad.

What's with "Parfait, McChicken, Salad"? Are those $1 too? Why is salad the biggest one? WHAT IS GOING ON?!?!

The campaign delivers the "Any Size" idea thru the copy message (i.e. errand vs. road trip, or snack wrap vs. Angus) and visually with the different cup sizes. I think it provides a clear message if you look at the campaign as a whole. By no means are we referring to calorie intake or the healthiness of the food. Here are the 4 size comparisons we used as well as the keylines for visual reference.

So there you have it. You can now sleep at night, safe in the knowledge that you (and your fellow GOOD readers) hold the key to this mysterious McDonald's ad.